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annual report 200717
Main pic:
Solvent drying
in the AuTEK
biomedical
screening
laboratory.
TECHNICAL REVIEW
GOLD INDUSTRY
AuTEK – extending the industrial uses of gold
Project AuTEK, the joint R&D initiative between Mintek and the three major
South African gold producers to develop new industrial uses for gold, is now
nanotechnology and biomedical applications.
AuTEK Biomedical
Biomedical research under Project AuTEK, jointly funded by Harmony Gold
and Mintek, focuses on developing new types of metal-based therapeutic
agents, with the emphasis on cancer, malaria, and HIV/AIDS. The past year
in the in-house team. Mintek’s HIV BSL II biomedical laboratory was fully
commissioned, and funding received
from the Technology and Human
Resources for Industry Programme
(THRIP) allowed for the acquisition
of a Nuclear Magnetic Resonance
(NMR) instrument, which will be
commissioned in early 2008. New
development opportunities are being
investigated through networking
and collaborative approaches
to the large pharmaceutical
companies, with the emphasis
on HIV.
More than 170 compounds
have been screened so far for
anti-tumour activity, with 30
per cent showing promising
results. Structure-based
design has resulted in an increase in the “hit rate” (activity plus
selectivity) to 10 per cent. The pharmacological work is largely
undertaken at the universities of Cape Town, Western Cape, and
Pretoria, with synthetic efforts taking place in-house and at three
local universities (Cape Town, Johannesburg, and KwaZulu-
USA for possible assistance with the further development of the
most promising compounds.
Under the HIV programme, more than 100 compounds were
screened in the past year (the majority of them in-house), with an
inhibitor rate of 16 per cent. Advanced studies on 19 interesting
candidates are under way, and it is planned to submit samples to
partners in the USA for further evaluation as a step towards pre-
clinical trials.
Steady progress has also been made in the anti-malarial
programme, which like the cancer programme is also largely
university-based. More than 40 ligands have been prepared, and
“Biomedical research
under Project AuTEK,
jointly funded by Harmony
Gold and Mintek, focuses
on developing new types
of metal-based therapeutic
agents, with the emphasis
on cancer, malaria, and
HIV/AIDS.”
annual report 2007 18
Pics from
top to
bottom:
The
biomedical
laboratory –
preparation
of in vitro
cell assays.
The Atomic
Force
Microscope
in the nano-
technology
centre.
A respirator
canister and
AUROliteTM
gold-based
catalyst.
Evaluating
precious-
metal-based
catalysts
for diesel
exhaust
after-
treatment
applications.
complexation studies are in progress. Initial data from screening
tests are expected in the last quarter of 2007.
To date, the AuTEK biomedical programme has produced two
PhD and three MSc graduates, and a further eight PhD, six MSc,
and four post-doctoral candidates are currently registered. Work
under the programme has won seven awards, and resulted in
100 contributions to professional journals and conferences, with
49 being international.
AuTEK Nanotechnology
The AuTEK nanotechnology programme, which is co-funded by
electrochemistry, molecular recognition (biolabelling), and
drug delivery systems. A novel method has been developed
for producing anisotropic precious-metal nanoparticles, and
further work is being carried out to control product quality, particle
size distribution, and reproducibility with the aim of imparting
desirable electronic, magnetic, optical, and catalytic properties.
Certain systems are being investigated for their possible use in
electrochemical sensors for the detection of glucose and other
biological structures.
The production of organically stabilised gold nanoparticles
for application in molecular recognition (biolabelling) has been
successfully scaled up to 2 litre batches. These will be stabilised and
functionalised by attaching bio-molecules, with the goal of developing
malaria, HIV, and diabetes. Similar technology involving multiplexing of the
underlying structure will be utilised to adapt the particles for drug delivery a
well as diagnostics.
To ensure that South Africa remains internationally competitive in this fast-
ordinated at national level by the Department of Science and Technology (DST)
through its National Nanotechnology Strategy. One of the main pillars of this
initiative is establishing a number of innovation centres around the country. Two
centres will be established in 2007, one at Mintek and the other at the CSIR. The
primary aims of the centre at Mintek are to train young scientists who will stimulate
the growth of an emerging nanotechnology industry in South Africa, develop
prototype products, and add value to the precious metals being produced locally.
The DST, the Medical Research Council, and the Water Research Commission
will be participating in the initiative, which will initially have three focal areas around
sensors, molecular recognition, and nanotechnology for the water industry.
AuTEK Catalysis
The AuTEK catalysis programme, which is co-sponsored by AngloGold Ashanti,
seeks to develop gold catalysts for industrial applications. One of the major hurdles to
establishing a gold catalyst market has been a lack of commercially viable quantities
of material for product testing and screening. Large-scale production of gold catalysts
is not easy, owing to issues such as gold particle size, reproducibility, and deactivation,
and involves synthesis techniques that are completely different to those currently
employed in PGM catalyst production. Research at AuTEK has been directed at
overcoming these hurdles and has led to the development of the AUROliteTM range of
gold catalysts.
Under the AuTEK catalysis programme, the current production capacity of 20 kg
per batch is currently being further scaled-up to the 65 kg scale to meet demand.
Construction of the plant, which is sponsored by the DST’s Precious Metals Initiative, is
annual report 200719
Pics from top to
bottom:
AUROliteTM
gold-based
catalyst.
Inspecting
emergency
equipment
during an ICMI
audit of a gold
plant.
Cyanide
speciation by
segmented
analysis.
Calibrating
a Cynoprobe
before
installation on a
gold plant.
expected to be complete by the fourth quarter of 2007.
AuTEK, in conjunction with the World Gold Council (WGC), is
actively marketing these gold-based catalysts under the trademark
AUROliteTM, and supplying end-users. The typical AUROlite
product range includes Au/Al2O3, Au/Fe2O3, Au/TiO2, Au/ZnO. Joint
marketing displays have been held at the North American Catalysts
Conference and Europacat – generating much interest, which has
translated into further orders. AUROlite materials have been supplied to
petrochemicals, oleochemicals, and respirators and other safety equipment.
Gold catalysts are unique in terms of their ability to catalyse oxidation
reactions at low temperature and/or by the use of molecular oxygen.
Examples of such reactions include:
• Carbon monoxide oxidation.
• Oxidation/selective oxidation of organics – e.g. glucose to gluconic acid,
cyclohexane to nylon precursors.
• Epoxidation – e.g. propene to propene oxide.
Gold catalysts have also been found to be suitable for the removal of mercury
from coal power plant emissions, and the hydrodechlorination (destruction) of
ground water pollutants such as trichloroethene.
Gold catalysts also offer the ability to oxidise the carbon monoxide in
hydrogen feedstock for fuel cells, converting it to “inert” carbon dioxide and
thereby preventing degradation of the cell’s performance. Mintek is still
seeking commercial partners to assist in the further development of this
technology, which has been tested at Johnson Matthey’s laboratories
and subsequently trademarked and patented under the name
AUROPureH2
TM.
Cyanide services
Mintek took part in full compliance audits of Sasol Polymers’
Sasolburg sodium cyanide plant and of Sasol Infrachem to assess
for compliance with the Producers’ and Transportation codes of the
International Cyanide Management Institute (ICMI). ICMI-based
“gap” audits were also undertaken at the Navachab gold mine in
Namibia and Geita in Tanzania. The audits planned for Iduapriem
and Bibiani in Ghana were re-scheduled, and will now take
place in 2007. Mintek takes the role of technical Expert Auditor
accreditation as Lead Auditor.
At the end of the year under review, the Cyanide Centre
Laboratory underwent an audit in terms of ISO 17025 (Testing
Laboratories), and Mintek expects to achieve full compliance with
this standard in mid-2007.
Mintek has built a solid foundation in soil, solution, and gas-phase
analysis and mass-balancing of cyanide, and is currently looking
at extending this expertise to other metals. As part of this process,
an advance gold-leach reactor is being commissioned that will
enable conditions such as agitation intensity, shear characteristics,
temperature, pressure, pH value, and redox potential to be
carefully monitored and controlled. The pulp can be sampled during
operation, with sub-samples taken for analysis and returned to the
leach without distorting the mass balance. Cyanide concentration and
species are monitored using the Cynoprobe on-line analyser, and a
SCADA system is used for data capture and trending. The new reactor
annual report 2007 20
Pics from top
to bottom:
Apparatus
for
determining
the rate
of oxygen
uptake
during gold
leaching.
Elution
the MINIXTM
gold-selective
resin.
The control
room in
Mintek’s
DC arc
demonstration
smelting
facility.
will initially be used in development work on high-arsenic gold
ores, incorporating arsenic speciation and mass-balancing. The
equipment will eventually form part of a comprehensive facility
for characterisation and problem-solving on gold leach and
adsorption circuits, from both the process and the environmental
aspects.
Process development
An extensive suite of testwork, including mineralogy,
comminution and gravity concentration, leaching, adsorption,
and carbon-in-pulp/carbon-in-leach (CIP/CIL) modelling, was
Gold’s Modder East project. On the commercial plant, which is
being designed by Bateman, about 40 per cent of the gold will
be extracted in a gravity circuit, with the remainder recovered by
CIL. The work showed that recoveries of between 87 per cent and
new gold mine on the East Rand in almost 30 years, is scheduled
to start production in the third quarter of 2009, and will reach a level
of 110 000 ounces (3.42 tons) a year at full output.
Laboratory testwork was conducted to evaluate processing options as
part of the feasibility study, carried out by MDM Engineering, for Mano
River Resources’ New Liberty gold project in Liberia. This project is
production targeted for the latter part of 2007.
A visit was paid to CVG Minerven in Venezuela to carry out a basic
Recommendations were made regarding options for upgrading the plants’
capacities and introducing new technology, as well as for tailings re-
treatment and cyanide management. Further work, including testing of a bulk
sample for process development, is anticipated in 2007.
The MINIXTM gold-selective resin was tested in a resin-in-leach (RIL) pilot plant
at Fairview gold mine, which was run by Gold Fields in collaboration with the
then owners of the mine. Gold Fields, who supply the Biox® technology used at
Fairview, are continuing work with Mintek to reduce the thiocyanate concentration
in the tailings. The MINIX resin was also tested successfully for scavenging
dissolved gold from slimes-dam return water at a Witwatersrand gold mine.
A number of service projects were carried out for projects in Botswana, the DRC,
Ghana, Mali, Romania, Zambia, and Zimbabwe, as well as South Africa. Ongoing
testing of surfactants (wetting agents) for application in heap leaching was conducted
in collaboration with the manufacturer. A new CIP/CIL and resin-in-pulp/resin-in-leach
(RIP/RIL) computer modelling programme was developed to interface with standard
Microsoft®Windows-based processes.
PLATINUM-GROUP METALS (PGM) INDUSTRY
Demonstration of the smelting step of the proposed ConRoast process for recovering
PGMs from high-chromium low-sulphur concentrates continued until the end of the year
under review. Four major DC furnace campaigns have now been conducted, treating a
total of 28 000 tons of revert tailings and other materials with Cr2O
3 contents of up to 5
per cent, at feed rates exceeding 1 000 tons per month. During the last campaign, which
ran continuously for 17 months, the availability of the furnace was 91 per cent.
The full ConRoast process involves the smelting of dead-roasted sulphide concentrates,
with recovery of the PGMs and base metals into an iron-based alloy rather than a sulphide
annual report 200721
Pics from top to
bottom:
A furnace tap
during the
ConRoast
smelting
campaign.
Flotation pilot
Pilanesberg
Pics 3 and 4:
The QEMSCAN
and Mineral
Liberation
Analyser
are used
extensively for
PGM process
development.
of ore types and concentrate compositions - it removes the limits
on the minimum quantities of contained base metals or sulphur, and
can tolerate the high chromite levels in concentrates characteristic
of UG2 ores without the necessity for copper cooling elements in the
furnace sidewalls.
of material was smelted in a 200 kilovolt-ampere DC arc furnace. A high
recovery was obtained, with 98% of the platinum, palladium, and rhodium
reporting to the iron alloy phase. An engineering feasibility study of the
process is under way, with Mintek providing design inputs for the proposed
commercial furnace.
Laboratory and pilot-plant testwork was carried out in support of the
feasibility study, by SRK Consulting, on Platmin’s Pilanesberg project. The
bench-scale testwork was conducted on diamond drill core samples and
the silicate and UG2 ores in industry-standard primary and secondary circuits,
were performed using ore from a trial pit excavated at the Tuschenkomst
property. The data generated during this work will be used to design the
processing plant, which will consist of separate concentrators for the silicate
ore and UG2.
A 60-ton representative sample from Ridge Mining’s Sheba’s Ridge project
was piloted to provide metallurgical design data for the feasibility study.
towards the pre-feasibility study (Annual Report 2006), with recoveries
of 86 per cent for copper, 69 per cent for nickel, and 73 per cent for
is scheduled for completion at the end of calendar 2007. According to
the pre-feasibility study, completed in March 2005, Sheba’s Ridge will
produce 24 000 ton of nickel, 12 000 tons of copper, and 390 000
ounces of PGMs and gold per annum.
Three pilot runs, plus extensive laboratory-scale work, were
completed on different ore types for Barrick Gold’s Sedibelo
project, and this work is continuing into 2007. Other investigations
were carried out for Sylvania Resources on the recovery of PGMs
from chromite tailings, and for AfriOre’s Akanani project (now
owned by Lonmin).
A considerable number of quantitative mineralogical
investigations, using the QEMScan and Mineral Liberation
characteristics of the PGMs, were carried out in conjunction with
the process development work. Mintek also worked closely with
the suppliers of both these technologies to increase the accuracy
of the results from rapid, automated scans of PGM-bearing
samples. This is a particular issue with the PGMs, because of the
overlap in spectral windows. In a new development, a quantitative
scanning electron microscope was set up on site at Mintek for
one of the major PGM producers. Mintek has been running the
instrument on the client’s behalf to provide prioritised mineralogical
support during studies of the various plant streams for mass-balance
purposes and other research projects.
As part of its research into more cost-effective comminution
technologies, Mintek commissioned a pilot-scale high-pressure grinding
annual report 2007 22
Pics from top
to bottom:
A pilot-scale
high-pressure
grinding
roll .
Pouring
molten
metal into
atomiser
cup.
Product from
roll (HPGR). This is a relatively new technology, which uses the
principle of interparticle crushing between two counter-rotating
conventional crushing in certain applications, the HPGR generates
a product with very favourable characteristics for downstream
processing, from incipient crack formation to complete particle
disintegration.
Testwork has been carried out on a number of ore types, mainly
from the PGM sector. While UG2 ores are generally too abrasive
for effective processing, considerable success has been realised
with Merensky ores. The results show that incorporating a HPGR
before the primary milling stage could lead to lower comminution
costs and enhanced metallurgical performance. Locked-cycle tests
to investigate whether the HPGR could in some instances replace
the primary milling circuit have indicated that a grind of 100 per cent
passing 600 micrometres can be achieved with a circulating load of
70 per cent. Mintek is planning to install a second, larger HPGR during
2007.
Phase 1 of a study in minor element deportment in PGM smelting,
which was conducted as part of the AMIRA P671 Project, was
completed. The results showed the need for further development of
analytical techniques, which would form a basis for the likely extension
of the project.
The Platinum Development Initiative (PDI) is a collaborative programme,
supported by the three major platinum producers, to develop new industrial
uses for platinum. The initial work of the programme focused on developing
platinum-based analogues of nickel-based superalloys. Experimental
phase-diagram work on the platinum-aluminium-chromium and platinum-
nickel-ruthenium systems has been completed, while the establishment of a
thermodynamic database for the platinum-aluminium-chromium-ruthenium alloy
system is almost complete. The outstanding phase diagram work will be done
at the University of the Witwatersrand under the Centre of Excellence in Strong
Materials.
The DST-funded programme for fast-tracking the commercialisation of platinum-
base superalloys has progressed according to plan. Three projects were initially
envisaged – the glass industry, coatings, and powder metallurgy. After a review, the
glass component was terminated, since it was felt that this project could not compete
with the well-established technology offered by the major players in the sector. A R2
million physical vapour deposition system has been commissioned for the coatings
work, which is being undertaken in collaboration with the University of the Free State
alloyed buttons produced at Mintek, and are being characterised at UFS as part of a
PhD study.
An Atomijet atomisation rig, capable of producing platinum powders in the size range
from 30 to 150 micrometres has been commissioned, and an uniaxial compaction press
is being re-furbished and should be delivered in the second half of 2007.
In September, six members of the PDI research team gave presentations at the
Japanese-South African-German Workshop and Summer School in Bayreuth, Germany.
This comprised a gathering of scientists from Germany, Japan, Russia and South Africa
FERROUS METALS INDUSTRY
The titaniferous magnetite layers in the Upper Zone of the Bushveld Complex contains
annual report 200723
Pics from top
to bottom:
Small-scale
smelting
titaniferous
magnetite.
Conducting
a ferronickel
smelting
campaign at
Mintek for
Oriel Resources
Plc.
A grinding ball
sectioned for
metallurgical
analysis.
SmartboltTM
austenitic
stainless steel.
vast resources of iron, vanadium, and titanium, but to date no
process has been developed that can economically recover
all three of these metals. The high titania levels make the ore
unsuitable for smelting in a traditional blast furnace, and the
and Vanadium, which operate the Mapochs Mine, processes the ore for
iron and vanadium, but discards the low-grade titanium slag.
Veremo Holdings has begun an evaluation of the feasibility of utilising
part of the titaniferous magnetite ore from the Bushveld Complex to
produce iron units that could be used as feed for foundries and steel plants.
The initial feasibility study includes the potential recovery of titania and
vanadium from the slag.
Approximately 5 tons of concentrate was produced from 14 tons of trenched
material and smelted in Mintek’s 200 kilovolt-ampere DC arc furnace.
The testwork was aimed at producing slag that could be used in further
development work, as well as evaluating the deportment of iron, titanium,
and vanadium under varied reducing conditions.
additions, the process could be controlled to produce good-quality iron with
high recoveries and a wide range of titania-containing slag compositions.
Further development work will investigate the feasibility of upgrading
2 and
recovering the vanadium from the slag.
Oriel Resources Plc (Oriel) has been engaged in developing its
Shevchenko Nickel project in Kazakhstan since 2004, and conducted a
major ferronickel smelting campaign at Mintek in 2005 (Annual Report
2005). Bateman was appointed in late 2004 to conduct a feasibility
study that was completed at the end of 2005 based on the work at
Mintek . The process includes an Aerofall mill and Polcal calciner
from Polysius, Germany, and the twin electrode DC arc furnace
is similar to the approach envisaged for the Koniambo ferronickel
project in New Caledonia, now owned by Xstrata.
Oriel has continued to develop the Shevchenko project and
to evaluate the selected process options so that the most
appropriate approach can be chosen for the project to proceed.
Mintek has been conducting additional testwork on these process
options for Oriel to assist with the project development.
In 2005, Mintek began a major collaborative project, funded
by the Innovation Fund and supported by Anglo Platinum, the
University of Pretoria, and an industrial partner, to develop
a more cost-effective grinding ball for the minerals industry.
Samples produced in laboratory-scale melts are undergoing
screening, and in parallel with this, reference balls are being
produced so that the casting methods can be optimised. Batch
tests of balls cast from the most promising materials are planned
Trials of the “smart” rockbolt, or SmartBoltTM, are continuing in
“highly critical” areas on two deep-level gold mines. Mintek is
working with a team of specialists towards the commercialisation of
both the SmartBolt and the HerculesTM low-nickel austenitic stainless
steel, and the Innovation Fund has indicated that it will support
commercialisation if the two projects merit it.
annual report 2007 24
Pics from top
to bottom:
Spiral
separation of
chromite.
Density
fractions of
an iron-ore
sample.
The
Sarcheshmeh
mine in Iran.
The project proposals and funding agreements for the ferrous
and base metals pillars of the Advanced Metals Initiative, which
quarter of 2007. Three projects have been proposed under this
initiative, all of which are aligned strongly with the automotive
industry.
An investigation was begun on the pre-reduction of manganese
ore and the possibility of recovering energy from the liquid slag.
These processes hold potential for reducing the carbon dioxide
emissions produced during smelting, and possibly for the
production of hydrogen.
Work continued on iron ore characterisation for Kumba
Resources in support of the Sishen Expansion Project. In
addition, investigations were carried out on the upgrading of
elutriation, and magnetic separation.
Metallurgical testwork, involving investigations of the size
distribution, comminution characteristics, washability using heavy
liquid separation, and gravity separation using tables and spirals,
was conducted on material from Chromex Mining’s Mecklenburg
chromite project. The results were used as input for the detailed
design and costing exercise, and to forecast the product split into
chemical, and foundry grade).
NON-FERROUS METALS INDUSTRY
The bioleaching work package under the European Union’s BioMinE
project, which is co-ordinated by Mintek, has continued to progress well.
During the year under review, a number of project partners investigated
the process engineering development, as well as the more fundamental
technology, related to the bio-hydrometallurgical treatment of two low-grade
Integrated pilot campaigns on the complex polymetallic concentrates from both
of these deposits is scheduled to begin at Mintek in the second half of 2007,
and will run through to mid-2008. It is anticipated that a number of our European
colleagues in BioMinE will participate in this programme, which, if successful, will
lead to pre-feasibility studies. Although the resources are of European origin, the
outcome of the work will be directly relevant to similar deposits in southern Africa
and in other parts of the world. BioMinE is funded under the EU’s Sixth Framework
Programme (FP6), and is also supported by a major strategic investment by the
DST.
Large-scale piloting of Mintek’s heap bioleaching technology for chalcopyrite-
bearing copper ores continued at the Sarcheshmeh Copper Complex in southern
2005, a further three 20 kt heaps were commissioned at approximately three-monthly
Copper Industries Company (NICICO) has decided to proceed with the development
of a commercial plant, with a capacity of 12 kt of copper metal per annum, at the
Dahrezar copper mine. Mintek will be contributing to the feasibility study for the project,
which is scheduled for completion towards the end of 2007, and will remain closely
involved in the engineering and commissioning of the planned commercial plant.
The successful heap bioleaching of chalcopyritic ores depends on the generation and
preservation of heat of chemical reaction in the heap, and prolonging the permeability
of the heap. These objectives have been realised by a combination of certain heap
construction features and operational tactics, and the life cycle of each heap has been
annual report 200725
Pics from top
to bottom:
Heap bio-
leaching at
Sarcheshmeh.
• Pregnant
leach solution
ponds.
• Pond under
construction.
• Inoculum
preparation
plant.
• Auger
sampling of
heap.
partitioned into several operating stages, each with its own targets
and criteria for completion. This approach has required a new
level of sophistication in heap leaching. For the Iranian pilot plant,
a spreadsheet-based operator advisory and administration system
has been developed, which tracks the life cycle of each individual cell
within a heap, and provides operator support for the most essential daily
decisions. These include the allocation of irrigant (intermediate leach
or to intermediate leach solution), and adjustment of the irrigation and
aeration rates to satisfy the stoichiometry of the reaction and maximise
heat accumulation within the heap. For commercial applications, a more
sophisticated package with additional features is being developed, that will
integrate with current industry-standard SCADA and database software.
As a result of the success at NICICO, Mintek has undertaken a considerable
amount of heap-bioleaching amenability testwork, which could lead to this
technology being further evaluated for application to low-grade copper, nickel
(sulphides and laterites), and uranium deposits in southern and central Africa.
Development continued on a novel technique for inoculating bacteria into
leach heaps, with the aim of obtaining a more rapid start-up and enhanced
oxidation rates, which will lead to higher heap temperatures and faster
copper leaching. A set of 6 m column leach tests were conducted on a low-
grade chalcopyrite ore, and further work is being conducted on techniques
to monitor the process. This project is being carried out with an industrial
partner, with funding from the Biotechnology Partnership and Development
(BioPAD) initiative.
Mintek is continuing with research on the development and optimisation
of molecular techniques for identifying the micro-organisms involved in
tank and heap leaching, in order to gain an improved understanding
vice
versa. Work at the University of the Free State and Rhodes University
on the production of precious-metal nanoparticles by biosynthesis
is focusing on the isolation of the proteins and enzymes involved,
with the aim of linking these to the varios sizes and shapes of
particles that are produced. A second round of THRIP funding has
been received for investigations into the bioleaching of silicate
minerals. Two MSc projects are under way, on nickel laterites (at
the University of KwaZulu-Natal) and the bio-assisted weathering
of kimberlites (at the University of the Witwatersrand), and will
be completed in March 2008. Two BTech projects are being
undertaken at Tshwane University of Technology on the biological
degradation of cyanide species.
In support of a study of a major expansion at the Nkomati
nickel mine, an 80 ton bulk sample of the Chromititic Peridotite
Mineralised Zone (PCMZ) was processed in Mintek’s milling and
The plant incorporated a scavenger cleaner circuit and employed
optimised residence times to enhance the recovery of the slow-
undertaken on a sample from the Main Mineralised Zone (MMZ).
ore, previously regarded as uneconomic, can be processed to
yield a saleable concentrate. This, together with improved metal-
price forecasts, made it possible to lower the cut-off grade applied to
portions of the resource, thus increasing the open-pit reserves.
As a result of applying the lower cut-off grades and including the
annual report 2007 26
Pics from top
to bottom:
Flotation
pilot-plant
campaign on
Nkomati ore.
The Nkomati
Nickel Mine
(photo
courtesy
Nkomati
Nickel).
Pilot-plant
operators
take samples
from the
manganese
solvent-
extraction
circuit
to purify
the cobalt
electrolyte
before
electro-
Copper
electro-
the KOV
PCMZ, Nkomati’s nickel reserves have increased by 50 per
cent – to 485 377 tons. The by-product reserves have also
43 per cent, and 4.181 million ounces of PGMs, a 70 per cent
increase. Based on these positive results, LionOre and ARM
commissioned DRA to proceed with a bankable feasibility study
for the large-scale expansion of the concentrator plants.
The proposed large-scale expansion, planned for 2010, will
incorporate mining of the PCMZ, increasing annual production
to approximately 20 000 tons of nickel and extending the life of
the mine to beyond 2020. An interim expansion exploiting the
disseminated MMZ will maintain nickel production at its current
level of about 5 000 tons per year after the massive sulphide
mineralisation is depleted in 2008.
Mintek has carried out process development work for a number
of copper-cobalt projects in Zambia and the DRC. Among these
a South African mining company in the DRC for many years. The
started up in September 2006. The second phase, which will involve
cobalt metal on-site at Ruashi, is under construction.
Mintek began bench and pilot work, which would be used in the bankable
feasibility study for phase II of the project, in April 2006. Three campaigns
were conducted, and the work was completed during March 2007.
In the design of the solvent-extraction and electrowinning circuit, Mintek
worked closely with Metorex’s design company, TWP Matomo Process
Plant. The plant has been designed for a capacity of 120 000 tons of ore per
month. When the phase II expansion is completed, production at Ruashi is
expected to increase to 45 000 tons of copper cathode and approximately 3
500 tons of cobalt metal and cobalt carbonate per annum.
A major process development campaign was conducted for the KOV copper-
cobalt project, also in the DRC. A total of 27 tons of material was delivered to
laboratory tests to determine the optimum leach conditions, integrated piloting of the
leaching, copper solvent extraction and electrowinning circuit, and Aspen simulation
LME Grade A standard (higher than 99.95 per cent copper), were produced. The KOV
complex, which contains one of the world’s largest high-quality copper and cobalt
resources, is being re-developed by Nikanor plc. The project will include a major
27 500 tons per year of cobalt products.
Dense-media separation, milling, and leaching testwork were carried out to investigate a
Green Team Consultants International.
Mintek has been involved in numerous projects to remove iron and manganese from
dilute cobalt sulphate solutions by oxidative precipitation using air/SO2. This technology
is attractive as it can be done at ambient temperature, relatively low pH, and ferrous
iron is quantitatively removed within 1-2 hours. In order to produce cobalt cathode of the
desired quality, iron, manganese, copper, zinc, and aluminium must generally be removed
from the feed to electrowinning. The requirements to produce an intermediate cobalt salt
are generally less stringent, but usually iron, aluminium, and manganese still need to be
removed.
annual report 200727
Pics from top to
bottom:
The Outotec
high-shear
impeller.
Laboratory
NicksynTM
reagent in
support of the
at Tali Nickel.
The thermal
Magnesium
Process demon-
stration plant.
The recent interest shown in this technology by emerging
copper-cobalt producers in central Africa has encouraged Mintek
to do some work to identify potential scale-up issues. Various
agitators and gas induction systems were investigated, and a high-
shear impeller designed and supplied by Outotec was selected for
further testwork on a 2 m3 scale to examine the effects of parameters
such as SO2
and temperature on the process. Optimisation tests remain to be done
on power consumption and various aspects around gas induction.
Two smelting campaigns were conducted on discard slag from BCL in
Botswana to compare the use of AC and DC furnaces for recovering
nickel and copper. The results showed that both technologies were equally
effective, and that the company could substantially improve the recoveries
in its slag-cleaning operation by adding reductant to the existing settling
furnaces.
The Mintek-developed nickel synergist (Nicksyn™) was evaluated to
optimise nickel recovery and nickel-calcium separation at Tati Nickel in
Botswana. Laboratory test work was conducted at Mintek on the feed to the
nickel solvent-extraction circuit to optimise the combination of the synergist
and the Versatic 10 commercial extractant, and the results applied on the
Activox® hydrometallurgical demonstration plant at Tati using a 0.5 ton
commercial batch of Nicksyn.
on the organic phase, which could result in gypsum formation in
the extraction circuit if the feed becomes saturated with calcium.
Previously, Tati Nickel minimised the problem by diluting the feed
stream with fresh water, but this would increase the size of the
production. Furthermore, with Versatic 10, the pH of extraction
cannot be increased as this causes higher calcium loadings -
extraction stages).
With the synergistic system, the calcium loading was about
one-tenth that obtained previously, and gypsum formation can
be completely avoided. The Versatic-Nicksyn combination also
achieved higher nickel recoveries (99.7 per cent compared
with about 99.3 per cent) using only four stages. In addition,
lower reagent losses were experienced, which can be ascribed
to the much lower pH of operation and the reduction in crude
formation.
Work continued on the production of titanium-aluminium master
alloys by aluminothermic reduction, and a project is in progress
at the University of Cape Town on the fundamental aspects of the
titanium-aluminium-oxygen-carbon-nitrogen system to determine
the best criteria for scale-up.
Following a review of the economics of the Mintek Thermal
Magnesium Process, Anglo American has decided not to pursue
commercialisation, since it is felt that it would not be able to
compete with the low-cost Chinese producers. Mintek will continue to
look for opportunities for applying the technology.
annual report 2007 28
Pics from top
to bottom:
Small-scale
pressure
leaching of
a uranium
contentrate.
uranium
leach liquor.
Uranium
oxide
precipitation.
Hydro-
phobicity
a diamond-
bearing
concentrate.
INDUSTRIAL MINERALS
ambient and pressure leaching, gold diagnostic leaching,
and CIL adsorption, was done for the Buffelsfontein tailings
recovery project owned by First Uranium, the gold and uranium
subsidiary of Simmer and Jack Mines. Based in this preliminary
to recover an uranium concentrate, then pressure leaching,
solvent extraction and ion exchange using NIMCIX continuous
leach residues would be treated in a CIL plant for gold recovery.
Also for First Uranium, pilot-scale leaching was conducted on a
bulk underground sample from the Ezulweni project to produce
a feed for solid-liquid separation, countercurrent decantation,
and ion-exchange testwork. The results will be used to generate
design criteria for a possible NIMCIX plant. Both these projects
are continuing into 2007.
Testwork was completed on the development of the process
Malawi, as part of the bankable feasibility study by GRD Minproc.
Paladin gave the go-ahead for the development of the project in
February 2007, and commissioning is scheduled for the third quarter
of 2008. Kayelekera will be Paladin’s second uranium mine in southern
Africa – Langer Heinrich in Namibia, for which Mintek conducted
2007.
Mintek’s uranium business continues to grow, and an increasing number
of approaches are being received concerning proposed projects on
Witwatersrand-type materials, particularly tailings re-processing for both
uranium and gold. Some of these are potentially very large projects. Mintek’s
strength in this area is the comprehensiveness of the services it can provide,
from initial investigations up to large scale piloting.
During the year, a new laboratory facility for characterising diamonds according
to their hydrophobicity (response to grease-table recovery) and luminescence
(recovery by X-ray methods) was fully commissioned. The laboratory has met with
an extremely favourable response form major industry players, including De Beers,
SouthernEra, and Bateman, and work on optimising recovery processes has been
done for a number of projects in South Africa and overseas. Mintek has engaged
an internationally recognised expert in kimberlite petrology and diamond studies,
and this project will be expanded in 2007/08 to include diamond characterisation for
purposes of marketing valuation and population discrimination.
Ongoing heavy-liquid separation testwork was carried out for De Beers to evaluate
Mintek’s capabilities in chlorination technology were further developed with the
can handle kilogram-size samples, resulting in a much-improved mass balance.
A suite of testwork, including sample characterisation, heavy-liquid separation, shaking-
conducted on a sample of bauxite. The aim of the work was to simulate a processing
annual report 200729
Pics from top
to bottom:
Personal
Protection
Equipment
(PPE) for
radiation
Monitoring a
bulk sample of
uranium ore.
Mintek’s HIV
Committee.
Access to
potentially
hazardous
areas is
restricted
to trained
personnel.
route to remove the quartz and hematite/goethite from the
material. It was found that around two-thirds of the total silica,
and more than half of the Fe2O
3, could be removed, which as well
as resulting in a higher-quality product, would reduce the formation
of “red mud” in the Bayer process.
QUALITY, ENVIRONMENT AND SAFETY
Mintek’s Environmental Management System underwent a successful
audit, for OHSAS 18001 (Occupational Health and Safety), will take place
in 2007, and that for IS0 9001 (Quality) the following year. Re-assessment
The Analytical Services laboratories underwent a successful surveillance
audit for ISO 17025 compliance in 2006.
At the end of the period under review, the Lost Time Injury Frequency Rate
(LTIFR) was 2.0, compared with the target of 1.0. The Client Dissatisfaction
Frequency Rate (CDFR), after consistently achieving the target of less
than 10, rose sharply in the second half of the year. This was due to late
delivery of results, and communication problems with the clients, on
several minor projects undertaken by one of Mintek’s divisions. Steps
have been taken to remedy these problems.
During 2006, two new indices were established: the Major
Environmental Incidents Frequency Rate (MEIFR) and Public
Dissatisfaction Frequency Rate (PDFR). Mintek’s MEIFR is above the
target of 5 at the moment. The upward trend is possibly the result of
as corrective action is implemented. The PDFR (which is a subset
of the MEIFR) is also above the target – however, the public
Mintek is registered as a uranium testwork facility with the NNR
and the Department of Minerals and Energy (DME). A Radiation
Protection Programme (RPP) has been incorporated as part of
the overall Safety, Health, and Environment programme, and
an internal audit schedule, incorporating site inspections by the
NNR, has been implemented.
“During the year, a new laboratory facility
for characterising diamonds according to their
hydrophobicity (response to grease-table recovery)
and luminescence (recovery by X-ray methods) was
fully commissioned.”
annual report 2007 30annual report 2007